You're mistaken. The message you posted is dated April 5. Talbot and Chew didn't meet with Governor Pickens and General Beauregard until April 8.
So? Obviously, the April 5th letter didn't address an April 8th meeting. It recorded an earlier meeting between the governor and Talbot where it was made clear that any ship that ignored warnings and approached the fort would be shot at. This earlier meeting is also documented in the Official Records in an April 4th letter by the other US attendee, Lt. G. W. Snyder. From that letter:
In compliance with your directions, I went, under a flag of truce, to the city of Charleston, in company with Captain Talbot, and had an interview with Governor Pickens and General Beauregard.